Page 1290 - Small Animal Internal Medicine, 6th Edition

1262 PART XII Oncology

(PCT), and malignant melanoma (MM); as discussed earlier, Cells in OSA occasionally have small to large pink cytoplas-
OSAs and CSAs can be composed of round cells, so they are mic granules (osteoid) (see Fig. 81.6 in Chapter 81). Cyto-
VetBooks.ir included within this category. RCTs are easily diagnosed on plasmic vacuoles are common in TVTs and HCTs.
Briefly, large cell LSAs are characterized by a monomor-
the basis of cytology; the presence or absence of cytoplasmic
granules or vacuoles and the location of the nucleus aid in
cells with large nuclei, a coarse chromatin pattern, and one
the classification of RCTs (see Fig. 74.3). phic population of individual poorly differentiated round
Cells in MCTs (Fig. 74.8), LGL LSAs (Fig. 74.9), and MMs or two nucleoli; occasional cells may be vacuolated (see Fig.
(Fig. 74.10) usually have cytoplasmic granules; cells in neu- 74.11). Small and intermediate cell lymphomas may be dif-
roendocrine tumors (i.e., thyroid carcinomas) can also have ficult to recognize cytologically because the neoplastic popu-
granules. When hematologic stains are used, the granules are lation may resemble normal lymphocytes. Cells in HCTs are
purple in MCTs; red in LGL LSAs; and black, green, brown, similar to those in lymphomas except that the chromatin
or yellow in MMs. Lymphomas (Fig. 74.11), HCTs (Fig. pattern is fine rather than coarse, they have more abun-
74.12), PCTs, and TVTs do not have cytoplasmic granules. dant cytoplasm, and they are frequently vacuolated (see Fig.

FIG 74.8 FIG 74.10
Photomicrograph of a fine-needle aspirate from a Photomicrograph of a fine-needle aspirate from a mass in
subcutaneous mass in an older Boxer with multiple the oral cavity of a 10-year-old Schnauzer. Note the dark,
dermoepidermal and subcutaneous masses and marked fine granules in the cytoplasm. The diagnosis was
multifocal lymphadenopathy. Note the monomorphic melanoma (×400).
population of round cells containing purple granules. The
cytologic diagnosis was mast cell tumor (×1000).

FIG 74.11
FIG 74.9 Photomicrograph of a fine-needle aspirate from the kidney
Photomicrograph of an impression smear from a mesenteric of a middle-aged Boxer with bilateral renomegaly. Note the
lymph node in an old cat evaluated because of vomiting monomorphic population of round cells, with large nuclei,
and diarrhea. Note the large round cells with red, large prominent nucleoli, and no cytoplasmic granules or
cytoplasmic granules. The diagnosis was lymphoma of large vacuoles. A mitotic figure is seen in the center. The
granular lymphocytes (×1000). cytologic diagnosis was lymphoma (×1000).